There is known an in-vehicle data-reproduction system which includes, in order that a passenger in a rear seat can enjoy video and music in a vehicle, a display that is placed on a ceiling and faced toward the rear seat, and a headphone for the passenger in the rear seat that receives an audio signal transmitted wirelessly from the display-side to thereby outputs a sound (see, for example, Patent Document 1).
Further, there is also a system in which a display is placed on a rear surface of a front seat in order not to interfere in rearward visibility of a driver. An example of this is shown in FIG. 11 and FIG. 12. As shown in FIG. 11, in a body unit 2 placed on the rear surface of a front seat 1, a panel unit 4 is stored with its display 7 being in a closed state. The panel unit 4 is coupled in openable and closable manner to the body unit 2 by a pair of hinge mechanisms 3, so that a viewer 50 in a rear seat pushes down a panel open switch 5 to release a lock between the panel unit 4 and a latch 6, and manually turns the panel unit 4 until the display 7 reaches an easily viewable angle for him/her as shown in FIG. 12. Further, an audio signal is transmitted by infrared light from an audio transmission unit 8 placed at an edge portion of the body unit 2, and a headphone 10 outputs as a sound, the audio signal of infrared light received by its audio reception unit 9.
In this configuration, since the audio transmission unit 8 is provided at the side of the body unit 2 where its design surface is placed, there is a problem that when a head position (that is, a position of the headphone 10) changes between an adult and a child as the viewers 50, it is difficult to surely receive the infrared light because of limitations in directional angle of transmitter elements 11a to 11c in the audio transmission unit 8 and in directional angle of a receiver element (not shown) in the audio reception unit 9. In order to solve that problem, conventionally, such a plurality of transmitter elements 11a to 11c are mounted on a special board 12 at their respective different angles as shown in FIG. 12, to thereby enlarge their transmission range. Thus, the number of the transmitter elements increases, resulting in degraded ease of assembly. In addition, because the front seat 1 is reclinable in many cases, and in that case, it is necessary to mount the transmitter elements 11a to 11c so that they accommodate not only to the difference in the head position of the viewer 50 but also to tilt angles due to reclining.
Here, a correspondence relationship between an adult viewer and directional angles 11a′ to 11c′ of the transmitter elements 11a to 11c is shown in FIG. 13, and a correspondence relationship between a child viewer 50 and directional angles 11a′ to 11c′ of the transmitter elements 11a to 11c is shown in FIG. 14. In FIG. 13 and FIG. 14, the transmitter element 11a, 11b and 11c of the audio transmission unit 8 can transmit infrared light within ranges of the directional angle 11a′, the directional angle 11b′ and the directional angle 11c′, respectively.
With respect to the adult viewer 50 whose position of the headphone 10 is high, when the front seat 1 is at a tilt angle as shown in FIG. 13 (a), the audio reception unit 9 mainly receives the audio signal of the transmitter element 11b (directional angle 11b′), whereas when the front seat 1 is tilted rearward by about 20 degrees so as to be at a tilt angle as shown in FIG. 13(b), the audio reception unit 9 mainly receives the audio signal of the transmitter element 11a (directional angle 11a′). On the other hand, as to the child viewer 50 whose position of the headphone 10 is low, when the front seat 1 is at a tilt angle as shown in FIG. 14(a), the audio reception unit 9 mainly receives the audio signals of the transmitter elements 11b, 11c (directional angles 11b′, 11c′), whereas when the front seat 1 is tilted rearward by about 20 degrees so as to be at a tilt angle as shown in FIG. 14(b), the audio reception unit 9 mainly receives the audio signal of the transmitter element 11a (directional angle 11a′). Accordingly, if the plurality of transmitter elements 11a to 11c is not mounted at their respective proper angles, there were cases where sufficient audio signal did not reach depending on the position of the headphone 10 and the tilt angle of reclining.
Meanwhile, in FIG. 12, since a recess portion 2a for storing the panel unit 4 is provided on the side of the body unit 2 where its design surface is placed, a circuit board (not shown) of the body unit 2 is provided in the back of the recess portion 2a. At the same time, the audio transmission unit 8 is required to be provided at the side of the body unit 2 where its design is placed. Thus, it is necessary to provide the special board 12 for the audio transmission unit 8 separately from the circuit board of the body unit 2, and to make connection between both of these boards using a lead wire 13 or the like.
On the other hand, in an automotive audiovisual system described in Patent Document 2, an infrared radiator for transmitting an infrared light beam (corresponding to the audio transmission unit 8) is fixed onto a console box placed near the elbow of the driver, or an overhead console provided on the ceiling of the automobile. Thus, there were cases where sufficient audio signal did not reach the headphone worn by the viewer from the infrared radiator because of interference by the seat due to change of the seat when, for example, it was slid or reclined.